sendEmail.js

// send email
function email(subject, body, col = "email") {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheets()[0];
  var selection = ss.getActiveRange();
  var currRow = selection.getRowIndex();
  var emailCol = getColByName(col);
  
  var email = sheet.getRange(currRow, emailCol).getValue();
  
  MailApp.sendEmail(email, subject, 'New Email', {
    replyTo: "",
    htmlBody: body
  });
}